A period is the name given to a horizontal row of the periodic table.
The periodic table has seven periods.
Apart from period 1, every period begins with an alkali metal and ends with a noble gas.
Period 1 contains only two elements: hydrogen and helium. Periods 6 and 7 are the longest periods, each containing 32 elements. Period 6 includes the lanthanides running from lanthanum to lutetium. Period 7 includes the actinides running from lanthanum to oganesson).